Instruction pipelining involves dividing the instruction cycle into multiple stages to allow multiple instructions to be processed simultaneously. The document discusses two-stage, four-stage, and six-stage pipelines and notes that pipeline hazards can occur when the actions of some pipeline stages must be stalled due to conditions like insufficient hardware resources to meet the simultaneous requirements of different instructions in the pipeline.

1. Instruction pipelining
An instruction pipeline consists of multiple sections each of which perform one of the
phases of the instruction cycle.
1. Two-stage pipeline
2. Four-stage pipeline
3. Six-stage pipeline

2. Two-stage pipeline

3. Speed-up

6. Pipeline hazards
• The pipeline operates continuously as long as the program does not encounter any
hazard situation.
• A hazard is a condition or situation in the pipeline due to which instruction
processing can not continue as usual in the predetermined clock cycle, and the
actions by some stages have to be stalled for some time, till the hazard disappears.
• The cause for the hazard can be either the hardware or the software.
• The hardware cause for hazard is the shortage of resources in meeting simultaneous
requirement of these, by various stages in pipeline, for different instructions in the
pipeline.
• This can be reduced by some extent if sufficient resources are added, though at
increased cost.